STUDIES ON THE DIGENETIC TREMATODES. A475 
Steringophorus cluthensis is Distomum pagelli 
v. Ben. ((Mém. Acad. Roy. Belg.,’ xxxviii (1871), Pl. IV, fig. 
17), from Sparus centrodontus. Van Beneden, unfor- 
tunately, gives absolutely no description of the species, but 
from his figure it seems probable that it is really a 
Steringophorus sp. It differs from Ster. cluthensis 
in having the ventral sucker three times as large as the oral 
sucker, the ovary globular, the yolk-glands extending behind 
testes, and the genital aperture further from the intestinal 
bifurcation. 
It is evidently a somewhat difficult matter to differentiate 
Steringophorus generically from Fellodistomum. The 
features which require to be emphasised in the former are: 
(1) the presence of a distinct cesophagus; (2) the absence of 
a protuberant genital papilla; (3) the situation of the genital 
aperture near the intestinal bifurcation instead of close in 
front of the ventral sucker; and (4) the presence of a true 
receptaculum seminis.’ These differences are not of great 
relative importance, and it is not at all impossible that the 
genera may eventually prove identical, in which case the 
name Steringophorus must be regarded as a synonym of 
Fellodistomum. 
Sub-fammily PLaciorcHin® Pratt, 1902. 
Genus Plagiorchis Liihe, 1899. 
Elaciorchis novabilis u.sp., Pl. 10; fig. 17. 
To the genus Plagiorchis have already been assigned well- 
nigh a dozen species, one or two of which can be differentiated 
from each other only with difficulty. They form on the whole 
avery homogeneous group. To these I have to add a form 
possessing such well-marked features that there can be no 
doubt of its specific distinctness. 
‘ According to Odhner there is no receptaculum seminis, but Miss 
Lebour (‘Fish Trematodes of the Northumberland Coast,’ p. 15) has 
shown that such a structure may actually exist in Steringophorus 
furciger. 
